diff --git a/src/xdiff/xinclude.h b/src/xdiff/xinclude.h
index 2928d329b..7d7b77b3e 100644
--- a/src/xdiff/xinclude.h
+++ b/src/xdiff/xinclude.h
@@ -29,7 +29,7 @@
 #include <string.h>
 #include <limits.h>
 
-#ifdef WIN32
+#ifdef GIT_WIN32
 #else
 #include <unistd.h>
 #endif